1. Field of the Invention
The present invention relates to a piezoelectric thin film device having an electromechanical conversion function and a manufacturing method for this piezoelectric thin film device, and an inkjet head and an inkjet recording apparatus.
2. Description of the Related Art
A common piezoelectric thin film device includes a lamination member provided by sandwiching a piezoelectric member, in the direction of its thickness, between two electrodes.
A polycrystal is usually employed as the piezoelectric thin film of such a device, and the crystal structure includes a plurality of crystal grains, which constitute the piezoelectric thin film, and grain boundaries, extant among the crystal grains. Various methods have been proposed to improve the structure to increase the piezoelectric characteristics. The affect produced by a defect in crystal grains, such as a lack of oxygen and the affect produced by the sizes of the crystal grains or the state of the grain boundaries, are especially regarded as factors for determining the superiority or inferiority of the withstand voltage characteristic of the piezoelectric thin film, and several views and improved proposals are disclosed, for example, in JP-A-2000-307163, JP-A-2001-237468 and JP-A-10-217458.
Also as described in JP-A-11-214763, in a case wherein very little or almost no foreign substance is present at grain boundaries, there is very little domain migration in the piezoelectric thin film, and the occurrence of gaps along the grain boundaries due to domain migration can be suppressed. However, orientation at the grain boundaries is discontinued with crystal grains, and further, according to the result obtained by the XRD analysis, a peak that it is not intended to be obtained, such as (110), is also observed. Furthermore, according to this description, precipitation of a compound, such as a PbO, that does not have a piezoelectric characteristic occurs at the grain boundaries.
One problem is that when a polycrystal is employed as a piezoelectric thin film, the voltage-strain characteristic (the displacement characteristic) of the piezoelectric thin film is such that linearity is inferior relative to the voltage application hysteresis. Another problem encountered when a polycrystal is used to form a piezoelectric thin film is that in a low field intensity area the displacement, relative to an applied voltage, is small, while in a high field intensity area the displacement is comparatively increased. And since a piezoelectric constant d31 is proportional to the displacement, a further problem is that the piezoelectric constant will not be steady relative to an applied voltage.